/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Configuration;
using Spring.Util;

namespace Spring.Objects.Factory.Config;

/// <summary>
/// Implementation of <see cref="IVariableSource"/> that
/// resolves variable name connection strings defined in
/// the standard .NET configuration file.
/// </summary>
/// <remarks>
/// <p>
/// When the &lt;connectionStrings&gt; configuration section is processed by this class,
/// two variables are defined for each connection string: one for connection string and
/// the second one for the provider name.</p>
/// <p>
/// Variable names are generated by appending '.connectionString' and '.providerName'
/// literals to the value of the <c>name</c> attribute of the connection string element.
/// For example:</p>
/// <pre>
/// <connectionStrings>
///    <add name="myConn" connectionString="..." providerName="..." />
/// </connectionStrings>
/// </pre>
/// <p>
/// will result in two variables being created: <b>myConn.connectionString</b> and <b>myConn.providerName</b>.
/// You can reference these variables within your object definitions, just like any other variable.</p>
/// </remarks>
/// <author>Aleksandar Seovic</author>
[Serializable]
public class ConnectionStringsVariableSource : IVariableSource
{
    private Dictionary<string, string> variables;

    /// <summary>
    /// Before requesting a variable resolution, a client should
    /// ask, whether the source can resolve a particular variable name.
    /// </summary>
    /// <param name="name">the name of the variable to resolve</param>
    /// <returns><c>true</c> if the variable can be resolved, <c>false</c> otherwise</returns>
    public bool CanResolveVariable(string name)
    {
        if (variables == null)
        {
            InitVariables();
        }

        return variables.ContainsKey(name);
    }

    /// <summary>
    /// Resolves variable value for the specified variable name.
    /// </summary>
    /// <param name="name">
    /// The name of the variable to resolve.
    /// </param>
    /// <returns>
    /// The variable value if able to resolve, <c>null</c> otherwise.
    /// </returns>
    public string ResolveVariable(string name)
    {
        if (variables == null)
        {
            InitVariables();
        }

        string retValue;
        variables.TryGetValue(name, out retValue);
        return retValue;
    }

    /// <summary>
    /// Initializes properties based on the specified
    /// property file locations.
    /// </summary>
    private void InitVariables()
    {
        variables = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        ConnectionStringSettingsCollection settings = ConfigurationManager.ConnectionStrings;
        foreach (ConnectionStringSettings setting in settings)
        {
            string providerName = setting.ProviderName;

            variables.Add(setting.Name + ".connectionString", setting.ConnectionString);
            variables.Add(setting.Name + ".providerName",
                StringUtils.HasText(providerName) ? providerName : "System.Data.SqlClient");
        }
    }
}
